County surcharge taxes and mail order

I recently went to a workshop given by the Florida Dept of Revenue,
and they talked about a discretionary county surcharge tax. In mail
order ads or ebay auctions I've seen people stating "Florida residents
add 6%" but I've never seen anyone address a county tax which is on
top of the 6% state tax. I assume the businesses just factor the
county taxes into the price and goes back through the various in-state
transactions and calculates the tax according to the county?